Flight control actuation system

ABSTRACT

A flight control actuation system comprises a controller, electromechanical actuator and a pneumatic actuator. During normal operation, only the electromechanical actuator is needed to operate a flight control surface. When the electromechanical actuator load level exceeds 40 amps positive, the controller activates the pneumatic actuator to offset electromechanical actuator loads to assist the manipulation of flight control surfaces. The assistance from the pneumatic load assist actuator enables the use of an electromechanical actuator that is smaller in size and mass, requires less power, needs less cooling processes, achieves high output forces and adapts to electrical current variations. The flight control actuation system is adapted for aircraft, spacecraft, missiles, and other flight vehicles, especially flight vehicles that are large in size and travel at high velocities.

GOVERNMENT RIGHTS

[0001] The invention described herein was made in the performance ofwork under NASA Cooperative Agreement No. NCC8-115, dated Jul. 1, 1996,and is subject to the provisions of Section 305 of the NationalAeronautics and Space Act of 1958 (42 U.S.C. 2457). The Government hascertain rights in this invention.

BACKGROUND OF THE INVENTION

[0002] This present invention relates generally to flight controlactuation systems and, more specifically, to a method and apparatus fora dual actuator control system, containing at least oneelectromechanical actuator and at least one pneumatic actuator. Thepresent invention concerns actuator systems for controlling flightcontrol surfaces on aircraft, spacecraft, missiles, and other flightvehicles.

[0003] Actuator servomechanism systems are used to manipulate flightcontrol surfaces to control flight direction, speed, inclination andother positional adjustments for flight vehicles. The actuator systemshave used mechanical, hydraulic, electrical, piezeoelectrical, andelectromechanical systems to apply force to the control surfaces. Forsafety, redundant parallel systems are used to independently maintaincontrol of the flight control surface in the event of failure of one ofthe actuator systems. One such parallel system is disclosed in U.S. Pat.No. 5,074,495 to Raymond. The hydraulically- and electrically-poweredactuators individually are capable of providing full actuation power.This system design does not account for significant variances from thenormal operational range of the electrically powered actuator, such ascontrol surface flutter and shockwave conditions. Flutter is oscillatorymotion between the vehicle frame and the control surface. Flutterincreases as the vehicle approaches resonant frequencies. Shockwaveconditions increase control surface loads as the vehicle approachessonic velocity. To account for the resultant high control surface loads,the actuator systems must be large in size and mass, negativelyimpacting flight vehicle weight constraints and aerodynamic envelopelimitations. Additionally, large flight vehicles traveling at highspeeds introduce risks of overloading the electrical actuator from thegreater forces needed to manipulate the flight control surfaces in suchsituations. To address these issues, power-assist systems were developedto amplify the force applied from the main control system and tominimize the control system resistance to movement. An example of such asystem is disclosed in U.S. Pat. No. 6,349,900 to Uttley, et al. Thisactuator system uses an electrical actuator assisted by a control tabmounted on the control surface. This system's drawbacks are lower outputforces than conventional actuator systems, and the excess size and massadded to the flight vehicle from the use of control tabs.

[0004] None of the prior art is specifically intended for lightweight,high-speed applications, and some suffer from one or more of thefollowing disadvantages:

[0005] a) excessive mass and size.

[0006] b) inability to accommodate flutter or shockwave effects.

[0007] c) increased cooling requirements.

[0008] d) low achievable output forces.

[0009] e) inferior aerodynamic envelope conditions.

[0010] f) inability to use detected electrical actuator currentvariations.

[0011] As can be seen, there is a need for an improved apparatus andmethod for a light, small, amplified flight control actuation system,which reacts well to flight extremes, such as high speeds and resonantfrequencies, does not require excessive cooling, provides high outputforces and adapts to detected electrical actuator current variations.

SUMMARY OF THE INVENTION

[0012] In one aspect of the present invention, a flight controlactuation system comprises a control means operable in response to aninput for generating a control signal, an electromechanical actuatorresponsive to the control signal, for operating a flight controlsurface, and a pneumatic actuator for assisting the electromechanicalactuator by reducing the load on the electromechanical actuator.

[0013] In another aspect of the present invention, a flight controlactuation system comprises a control means operable in response to aninput for generating a control signal, an electromechanical actuatorresponsive to the control signal, for operating a flight controlsurface, and a pneumatic actuator for assisting the electromechanicalactuator by reducing the load on the electromechanical actuator, whereinthe pneumatic actuator initializes when the current in theelectromechanical actuator increases beyond a predetermined amperage.

[0014] In a further aspect of the present invention, a flight controlactuation system for a flight vehicle comprises at least one flightcontrol surface. An electromechanical actuator system is adapted to acton each flight control surface, and a pneumatic actuator system isadapted to produce a force to act on at least one of the flight controlsurfaces. At least one electromechanical actuator is associated with adistinct one of the at least one flight control surfaces and acontroller adapted to produce an electrical signal for controlling atleast one of the flight control surfaces. An electrical circuit isconnected to the at least one electromechanical actuator which isadapted to receive the electrical signal, to control the position of theelectromechanical actuator with the electromechanical actuator adaptedto move in response to the electrical signal. The pneumatic actuatorsystem is solely associated with the at least one electromechanicalactuator, the pneumatic actuator system comprising a piston, a pressurevessel, an exhaust valve, a pressurization solenoid valve, a checkvalve, a manifold, a pressure switch, the valves adapted to receive theelectrical signal and to route a pneumatic pressure to an actuationdevice adapted to receive the pneumatic pressure and produce a pneumaticforce to continuously actuate the distinct one of the aerodynamic flightcontrol surfaces of the flight vehicle in response to the electricalsignal.

[0015] In another aspect of the present invention, a method is alsodisclosed for operating a flight control actuation system, the systembeing adapted to activate at least one pneumatic actuator in response toat least one signal produced by a control surface actuation signalsystem for positioning at least one control surface. The methodcomprises the steps of (a) receiving an input signal in the form of aposition demand providing an instruction for deflecting a controlsurface to a new position and (b) the controller generating acorresponding control signal for operating an electromechanicalactuator. In addition the method comprises the steps of (c) receiving afeedback signal in the form of an electrical current measurement at theelectromechanical actuator, (d) comparing the electrical currentmeasurement to a predetermined electrical current value, and (e) thecontroller generating a corresponding pressurization control signal foroperating a pneumatic actuator for reducing the load on theelectromechanical actuator.

[0016] In yet another aspect of the present invention, a method foroperating a flight control actuation system comprises the steps of (a)operating a flight vehicle, (b) receiving a flap demand instruction, and(c) comparing the position demand with output from a control surfaceposition sensor. In addition the method comprises the steps of (d)generating an actuator position demand to at least one electromechanicalactuator, (e) monitoring the electromechanical actuator electricalcurrent load, comparing the electrical current load with a predeterminedelectrical current load limit, (f) closing at least one exhaust valve,(g) opening at least one pressurization solenoid valve whenever theelectromechanical actuator current is more than the predeterminedelectrical current load limit, and (g) closing a pressurization solenoidvalve whenever the electromechanical actuator electrical current loaddecreases below the predetermined electrical current load limit.

[0017] These and other aspects, objects, features and advantages of thepresent invention, are specifically set forth in, or will becomeapparent from, the following detailed description of a preferredembodiment of the invention when read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]FIG. 1 is a schematic of the controller-driven actuation systemacting on a flight control surface according to an embodiment of thepresent invention; and

[0019]FIG. 2 is a schematic of a pneumatic actuation system according toan embodiment of the present invention;

[0020]FIG. 3 is a perspective view of an X-33 flight vehicle with aflight control actuation system according to an embodiment of thepresent invention;

[0021]FIG. 4 is a perspective view of an electromechanical actuator anda pneumatic actuator, both actuators acting on the same flight controlsurface, according to an embodiment of the present invention;

[0022]FIG. 5 is a graph of body flap load and body flap extension lengthversus time, according to an embodiment of the present invention;

[0023]FIG. 6 is a graph of actuator rate versus actuator force,comparing the power demands of a sole electromechanical actuator and thesystem of the present invention using an electromechanical actuator anda pneumatic actuator, according to an embodiment of the presentinvention;

[0024]FIG. 7A is a graph of a measurement of electromechanical actuatorelectric current versus time, according to an embodiment of the presentinvention;

[0025]FIG. 7B is a graph of body flap load moment versus time, accordingto an embodiment of the present invention;

[0026]FIG. 7C is a graph of electromechanical actuator torque versustime, according to an embodiment of the present invention;

[0027]FIG. 7D is a graph of pneumatic actuator torque versus time,according to an embodiment of the present invention;

[0028]FIG. 8 is a flowchart demonstrating the function and operation ofthe pneumatic supply module, according to an embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0029] The following detailed description is of the best currentlycontemplated modes of carrying out the invention. The description is notto be taken in a limiting sense, but is made merely for the purpose ofillustrating the general principles of the invention, since the scope ofthe invention is best defined by the appended claims.

[0030] The present invention may comprise a position controlledactuation system to accurately position a control surface while using anauxiliary actuation system to provide a load trim function for theposition controlled actuation system. The present invention may allowthe use of an auxiliary actuator to provide a large portion of the forceto control the actuation system position. This may limit the smallerportion of the load, provided by a positioning actuator, to a level thatis within the capability of a relatively low power positioning actuator.

[0031] The invention is useful for controlling all types of flightvehicles, including, but not limited to, aircraft, missiles (includingmissile thrust vector controls), and spacecraft. One example of a use inspacecraft is depicted in FIG. 3. The X-33 flight vehicle 250 is aone-half-scale suborbital prototype for a proposed single-stage-to-orbitreusable launch vehicle. In flight tests, the X-33 flight vehicle 250will accelerate to a maximum speed of Mach 16 and climb to an altitudeof about 250,000 feet. The X-33 flight vehicle 250 may have four typesof flight control surfaces: rudders 260, X-33 flight vehicle body flaps270A and 270B, outboard elevons 280, and inboard elevons 290. Each ofthe flight control surfaces can be independently actuated with at leastone electromechanical actuator (FIG. 1, 210A). For example, as shown inFIG. 3, a rudder actuator 180 may be situated to operate on rudder 260.Likewise a left outboard elevon actuator 200 may operate on the leftoutboard elevon 280 and the left inboard elevon actuator 190 may operateon the left inboard elevon 290. Left body flap pneumatic actuator 11Aand right body flap pneumatic actuator, 11B may supplement the X-33 bodyflap electromechanical actuator 210A and 210B forces to assist X-33flight vehicle body flap 270A and 270B actuation, as shown in FIG. 3. Apneumatic actuator may be used to assist actuation of any of the flightcontrol surfaces available. For illustrative purposes, the followingdescription is of an aircraft, however, it is to be understood thatother flight vehicles can be substituted for the aircraft.

[0032] The present invention generally provides a flight controlactuation system (FIG. 1, 10) that may include an electromechanicalsubsystem that can independently control a flight control surface. Theelectromechanical subsystem may be associated with a pneumatic subsystemthat may assist in controlling the flight control surface when needed.When the electrical current on the electromechanical actuator 210Asurpasses a predetermined limit, the pneumatic system may activate underthe direction of a controller. This is unlike the prior art, whichrelies on redundant actuation systems of large mass and size, which arevulnerable to flutter and shockwave phenomena, require heavy coolingsystems, are unable to respond to electrical current load variations,produce low output forces, negatively impact aerodynamic envelopeconditions, and fail to adjust to electromechanical overload conditions.

[0033] Referring to FIG. 1, there is shown a flight control actuationsystem 10, according to the present invention, for manipulating anaircraft flight control surface, such as an aileron, a wing or bodyflap, a slat, a flaperon, an elevator, a spoiler, or a rudder. In thepresent example, the flight control surface is a body flap. Thefollowing discussion applies equally to the left body flap (FIG. 3,270A) and right body flap (FIG. 3, 270B).

[0034] The flight control actuation system 10 comprises a left body flapcontroller 80A, which may be installed on a flight vehicle, as shown inFIG. 3. The left body flap controller 80A may be located within theaircraft frame. The left body flap controller 80A may be connected to anelectromechanical actuator 210A, which may be mounted in a position toexert a force on the left body flap 270A. The flight control actuationsystem 10 may operate as a servomechanism, where left body flapcontroller 80A may be situated to receive an input signal in the form ofa position demand that may provide an instruction for manipulating theleft body flap 270A. The left body flap controller 80A may generate acorresponding actuator position demand, as shown in FIG. 1, foroperating the electromechanical actuator 210A, in response to theposition demand. The left body flap controller 80A may be arranged toreceive feedback signals that indicate movement of the left body flap270A for generating control signals. Particularly, a control surfaceposition sensor 150 mounted between the aircraft body 160 and the leftbody flap 270A may be arranged to send electrical signals to the leftbody flap controller 80A, which may indicate the left body flap 270Aposition in relation to the original closed position of left body flap270A and the body flap acceleration. Alternatively, an electromechanicalactuator position sensor 170 may be mounted externally or internally tothe electromechanical actuator, and may be arranged to send anelectrical signal representing the left body flap 270A position and/orthe linear stroke position of the electromechanical actuator 210A to theleft body flap controller 80A. The control surface position sensor 150and the electromechanical actuator position sensor 170 may be rotary orlinear variable differential transformers, potentiometers, Hall effectdevices, or other generally known suitable devices.

[0035] The left body flap controller 80A may be arranged to receive aninput signal in the form of a position demand providing an instructionfor deflecting the left body flap 270A to a new position. The positiondemand may be generated by a pilot, a computer, or a remote controldevice. Upon receipt of the position demand, the left body flapcontroller 80A may monitor the position and acceleration signals fromthe control surface position sensor 150 and/or the electromechanicalactuator position sensor 170 and may generate an actuator positiondemand signal representing a new stroke position for theelectromechanical actuator 210A. The response of the electromechanicalactuator 210A may be to adjust the position of the left body flap 270Aby extending or retracting the shaft to exert a force on the left bodyflap 270A to move the body flap in the commanded direction. The leftbody flap 270A then may move to a new position.

[0036] The behavior of the present invention can be further understoodby reference to the graph in FIG. 5, which describes the relationshipbetween body flap load and body flap extension length versus time. Asthe load on the electromechanical actuator 210A increases, the left bodyflap controller 80A may activate the pneumatic system to cause the leftbody flap pneumatic actuator 11A to act on the left body flap 270A toassist the electromechanical actuator 210A in absorbing the load on leftbody flap 270A. In this example, as the left body flap pneumaticactuator 11A initiates, the load on the electromechanical actuator 210Amay fall to values substantially below 18,000 pounds. The load on theelectromechanical actuator 210A may peak at approximately 100,000 poundsof force, without assistance from the left body flap pneumatic actuator11A, which may activate during the first 100 seconds of operation. FIG.6 demonstrates the difference between the force requirements when usingonly the electromechanical actuator 210A and using the presentinvention, comprising the use of the combination of theelectromechanical actuator 210A and left body flap pneumatic actuator11A to assist during increased flap load conditions. The motorcapability plot 240 may indicate the capability of the electrical motor(not shown) that operates the electromechanical actuator 210A. When theforce is zero, the maximum no-load rate point A may correspond to themaximum attainable speed of the electrical motor. Point F represents themaximum stall load (at zero rate), which must be resisted to hold theflight control surface in its desired position and prevent the surfacefrom returning back to a neutral position (position before extending thesurface). Point B may be the maximum force condition that combines aload that may be substantially less than the maximum stall load F withhigh motor rate.

[0037] Under normal flight conditions, when the body flap load may below, for example, under 18,000 pounds force and 40 amps, the left bodyflap pneumatic actuator 11A, attached to the left body flap 270A, maynot be in use. The body flap performance plot 230 indicates the range ofpower needed to operate a left body flap 270A. The ideal power condition(when using only the electromechanical actuator 210A) may be at the bodyflap specification point C. E, the body flap performance limit point,may be the extreme condition of the body flap performance limit point,while the intermediate point may be the location of the body flapperformance mid-point D. Using only the electromechanical actuator 210Amay not be optimal, as the majority of the body flap performance, asrepresented by the length of the body flap performance plot 230, occursoutside the capability of the motor, as represented by the motorcapability plot 240. However, when the left body flap pneumatic actuator11A combines with the electromechanical actuator 210A, the electricalmotor operates at the dotted line G extending vertically down from themaximum force condition B. The amount of force at this point, 18,000pounds may be the maximum electromechanical actuator force requirementto extend the left body flap 270A, using the present invention. Theshaded portion H indicates the added capability on the left body flap270A with the electromechanical actuator 210A and the left body flappneumatic actuator 11A in combination.

[0038]FIGS. 7A, 7B, 7C, and 7D depict the electrical current behavior inrelation to the load, and actuator torques. In FIG. 7A, the electricalcurrent initially increases to about 40 amps, then drops to negativevalues (up to about −30 amps), then level out to values of about 0 amps.FIG. 7B shows how the load increases substantially steadily until aboutthe point where the electrical current changes from positive amperage tonegative amperage. The load decreases substantially afterwards. In FIG.7C, the torque on the electromechanical actuator 210A exhibits behavioranalogous to the behavior of the electrical current (initiallyincreasing, substantially decreasing, then settling to substantiallyzero). In FIG. 7D, the pneumatic torque may initially be at zero,indicating that the left body flap pneumatic actuator 11A may not yet beactivated. When the electrical current, as shown in FIG. 7A, reachesabout 40 amps, then the left body flap controller 80A sends a pneumaticload assistance requirement, as shown in FIG. 1. As the left body flappneumatic actuator 11A activates, the pneumatic torque increases in anegative direction, as shown in FIG. 7D, along with the increasing loadshown in FIG. 7B. As the pneumatic torque reaches a peak value (FIG.7D), the electromechanical torque decreases (FIG. 7C), the electricalcurrent markedly decreases (FIG. 7A) and the load peaks beforediminishing. As can be seen by the FIGS. 7A-7D, the combination of theleft body flap pneumatic actuator 11A with the electromechanicalactuator 210A enables effective control of the left body flap 270A whilelimiting the maximum load on the electromagnetic actuator 210A withincreasing left body flap 270A loads. The controller activates left bodyflap pneumatic actuator 11A when the electromechanical actuator 210Aelectrical current exceeds 40 amps, to assist the manipulation of leftbody flap 270A by the electromechanical actuator 210A.

[0039] In extreme flight conditions, for example high-speed flight orlarge aircraft mass or size, the force needed to adjust the left bodyflap 270A position may be substantial, requiring substantial electriccurrent to the electromechanical actuator 210A. This normally wouldrequire an electromechanical actuator 210A of substantial size and mass.However, using an electromechanical actuator 210A that may be too largewould affect negatively the aerodynamic envelope. Furthermore, a massivedevice would negatively affect the maximum flight weight limit and themaneuverability of a flight vehicle. Instead, the present inventioncomprises a controller that may be adapted to use a more compact,lighter electromechanical actuator 210A. When the electrical currentload on the electromechanical actuator 210A increases past apredetermined maximum limit, based on the capability of theelectromechanical actuator 210A, the left body flap controller 80A mayproduce a signal to pressurize the left body flap pneumatic actuator11A, to apply force to the left body flap 270A by reducing the load onelectromechanical actuator 210A and to assist in manipulating theposition of the left body flap 270A.

[0040]FIG. 4 shows in more detail the electromechanical actuator 210Aand the left body flap pneumatic actuator 11A acting on left body flap270A. The electromechanical actuator 210A may be operated by anelectrical motor (not shown), while the pneumatic supply module (FIG. 2,120) constitutes a separate pneumatic system that powers the left bodyflap pneumatic actuator 11A. Using only the electromechanical actuator210A to manipulate the left body flap 270A would not be sufficient underconditions where the left body flap 270A loads cause theelectromechanical actuator 210A current to exceed 40 amps. The combinedeffect of the force applied by the combination of the electromechanicalactuator 210A and the left body flap pneumatic actuator 11A may acttogether to produce sufficient force to manipulate the left body flap270A even in high-speed aircraft, missiles, or other high demand flightvehicles. The use of the left body flap pneumatic actuator 11A mayenable the use of an electromechanical actuator 210A of low output, withlow power requirements, low mass and small size.

[0041] Referring now to FIG. 2, a schematic view of the pneumaticportion of the flight control actuation system 10 is shown. Thepneumatic portion of the flight control actuation system 10, which isfurther addressed below, may comprise one or more left body flappneumatic actuators 11A, one or more left body flap controllers 80A, andone or more pneumatic supply modules 120. As explained above, the leftbody flap controller 80A may direct the operation of the left body flappneumatic actuator 11A to assist an electromechanical actuator 210A inthe manipulation of the left body flap 270A. The left body flappneumatic actuator 11A may contain a left pneumatic actuator piston 20Aand an actuator vent 30. The gas to provide the pneumatic force for theleft body flap pneumatic actuator 11A may be provided by the pneumaticsupply module 120 through the use of a pressure vessel 40 that storeshigh pressure gas, for example, nitrogen. A manifold 100 may be coupledto the mouth of the pressure vessel 40 for directing the flow ofpressurized gas from the pressure vessel 40 to pressurization solenoidvalves 50 which control the gas feed to the left and right body flappneumatic actuators 11A, 11B. Vent solenoid valves 60 control theventing of gas from the left and right body flap pneumatic actuators11A, 11B. At least one pressure switch 90 and at least one check valve110 may aid in servicing the pressure vessel 40.

[0042] A logic flow diagram in FIG. 8 further displays the function andoperation of the pneumatic supply module 120. Left body flap controller80A may be connected by wires to the electromechanical actuator 210A todetermine the actuator's electric current. Positive amperage mayindicate a compressive condition in the electromechanical actuator 210Awhile negative amperage may indicate tension in the electromechanicalactuator 210A. If the electric current does not exceed the electricalcurrent load upper limit, for example, +40 amps, as shown in FIG. 7A,then electromechanical actuator 210A continues to operate withoutassistance from the left body flap pneumatic actuator 11A. If theelectrical current does exceed +40 amps, then the vent solenoid valve 60may close and the pressurization solenoid valve 50 may open. When theelectrical current falls below +40 amps, the pressurization solenoidvalve 50 may close. If the electric current falls below the lower limit,for example, zero amps, the vent solenoid valve 60 may open. When theelectrical current rises above the lower limit, the vent solenoid valve60 may close. The process shown in FIG. 8 may repeat as necessary tomaintain the electromechanical current between the upper and lowercurrent limits.

[0043] The pneumatic supply module 120 may comprise separatepressurization solenoid valves 50 and vent solenoid valves 60 to controlpressure to the left and right body flap pneumatic actuators (11A and11B, respectively), supplied by at least one pressure vessel 40. Thepressurization solenoid valve 50 may act as the closure valve to thepressure vessel 40, being spring-loaded closed so as to not provideforce to the left body flap pneumatic actuator 11A or the right bodyflap pneumatic actuator 11B when the system does not need assistancefrom the left or right body flap pneumatic actuators 11A, 11B.

[0044] Although the present invention has been described in considerabledetail with reference to certain preferred versions thereof, otherversions are possible. Therefore, the spirit and scope of the appendedclaims should not be limited to the description of the preferredversions contained therein.

We claim:
 1. A flight control actuation system for use in a flightcontrol system comprising: a controller operable in response to an inputfor generating a control signal; an electromechanical actuatorresponsive to the control signal, for operating a flight controlsurface; and a pneumatic actuator for assisting the electromechanicalactuator by reducing the load on the electromechanical actuator.
 2. Theflight control actuation system of claim 1, wherein theelectromechanical actuator and the pneumatic actuator are attached tothe same flight control surface.
 3. The flight control actuation systemof claim 2, wherein the flight control surface comprises at least oneaileron.
 4. The flight control actuation system of claim 2, wherein theflight control surface comprises at least one flaperon.
 5. The flightcontrol actuation system of claim 2, wherein the flight control surfacecomprises at least one elevator.
 6. The flight control actuation systemof claim 2, wherein the flight control surface comprises at least onespoiler.
 7. The flight control actuation system of claim 2, wherein theflight control surface comprises at least one rudder.
 8. The flightcontrol actuation system of claim 1, comprising at least one pressurevessel for supplying gas to the pneumatic actuator.
 9. The flightcontrol actuation system of claim 1, comprising at least one ventsolenoid valve connected to the pneumatic actuator.
 10. The flightcontrol actuation system of claim 1, comprising at least onepressurization solenoid valve connected to the pneumatic actuator. 11.The flight control actuation system of claim 9, comprising at least onepressurization solenoid valve connected to the pneumatic actuator andconnected to the vent solenoid valve.
 12. A flight control actuationsystem for use in a flight control system comprising: a controlleroperable in response to an input for generating a control signal; anelectromechanical actuator responsive to the control signal, foroperating a flight control surface; a pneumatic actuator for assistingthe electromechanical actuator by reducing the load on theelectromechanical actuator; wherein the pneumatic actuator initializeswhen the electrical current in the electromechanical actuator exceeds apredetermined amperage.
 13. The flight control actuation system of claim12, comprising at least one vent solenoid valve and at least onepressurization solenoid valve connected to the pneumatic actuator. 14.The flight control actuation system of claim 13, wherein the controllercloses the pressurization solenoid valve when the electrical currentdecreases below the predetermined amperage.
 15. The flight controlactuation system of claim 12, wherein the predetermined amperage in theelectromechanical actuator is 40 amps positive.
 16. The flight controlactuation system of claim 13, wherein the predetermined amperage in theelectromechanical actuator is 40 amps positive.
 17. The flight controlactuation system of claim 13, wherein the controller opens the ventsolenoid valve when the electrical current decreases below 10 ampsnegative.
 18. A flight control actuation system for use in a flightcontrol system comprising: at least one aerodynamic flight controlsurface; an electromechanical actuator system adapted to act on eachaerodynamic flight control surface; a pneumatic actuator system adaptedto produce a force to act on at least one of the aerodynamic flightcontrol surfaces; at least one electromechanical actuator associatedwith a distinct one of the at least one aerodynamic flight controlsurfaces; a controller adapted to produce an electrical signal forcontrolling at least one of the aerodynamic flight control surfaces; anelectrical circuit connected to the at least one electromechanicalactuator with at least one electromechanical actuator adapted to receivethe electrical signal; the pneumatic actuator system solely associatedwith the at least one electromechanical actuator; the pneumatic actuatorsystem comprising; a piston; a pressure vessel; a vent solenoid valve; apressurization solenoid valve; and a pressure switch; the vent solenoidvalve and pressurization solenoid valve adapted to receive theelectrical signal to route a pneumatic pressure; an actuation deviceadapted to receive the pneumatic pressure and produce a pneumatic force;and the actuation device being adapted to continuously actuate thedistinct one of the aerodynamic flight control surfaces of a flightvehicle in response to the pneumatic force.
 19. The flight controlactuation system of claim 18, wherein a control surface position sensordetects position information from the aerodynamic flight control surfaceand sends the information to the controller.
 20. The flight controlactuation system of claim 18, wherein an electromechanical actuatorposition sensor detects position information from the electromechanicalactuator and sends the information to the controller.
 21. The flightcontrol actuation system of claim 18, wherein the stroke length of theelectromechanical actuator is substantially the same as the strokelength of the pneumatic actuator stroke length.
 22. The flight controlactuation system of claim 18, wherein the electromechanical actuatorcomprises a piezoelectric crystal.
 23. A method for operating a flightcontrol actuation system, the system being adapted to activate at leastone pneumatic load assist actuator in response to at least one signalproduced by a control surface actuation signal system for positioning atleast one control surface, the method comprising the steps of: receivingan input signal in the form of a position demand providing aninstruction for deflecting a control surface to a new position;generating a corresponding control signal for operating anelectromechanical actuator; receiving a feedback signal in the form ofan electrical current measurement at the electromechanical actuator;comparing the electrical current measurement to a predeterminedelectrical current value; and, generating a corresponding control signalfor operating a pneumatic actuator for reducing the load on theelectromechanical actuator.
 24. The method of claim 23, comprising afurther step wherein the pneumatic actuator vents and relieves forcewhen the electromechanical actuator tension load increases.
 25. Themethod of claim 23, wherein the electromechanical actuator and thepneumatic actuator are attached to the same flight control surface. 26.A method for operating a flight control actuation system comprising thesteps of: operating a flight vehicle; receiving a flight control surfaceposition demand instruction; comparing the position demand with outputfrom a control surface position sensor; generating an actuator positiondemand to at least one electromechanical actuator; monitoring theelectromechanical actuator electrical current load; comparing theelectrical current load with a predetermined electrical current loadlimit; closing at least one vent solenoid valve; opening at least onepressurization solenoid valve whenever the electromechanical actuatorcurrent is more than the predetermined electrical current load limit;and closing a pressurization solenoid valve whenever theelectromechanical actuator electrical current load decreases below thepredetermined electrical current load limit.
 27. The method of claim 26,further comprising the step of: opening at least one vent solenoid valvewhenever the electromechanical actuator current is negative.
 28. Themethod of claim 26, further comprising the step of: closing at least oneexhaust valve whenever the electromechanical actuator current ispositive.
 29. The method of claim 26, further comprising the step of:opening at least one exhaust valve and closing at least onepressurization solenoid valve during a failure condition.
 30. The methodof claim 26, further comprising the step of generating a pneumatic loadassistance requirement instruction to at least one pneumatic loadassistance device, for manipulating a flight vehicle control surface.31. The method of claim 26, wherein the flight vehicle is an aircraft.32. The method of claim 26, wherein the flight vehicle is a spacecraft.33. The method of claim 26, wherein the flight vehicle is a missile.